A toilet seat assembly of this type is manufactured by the Applicant. It has the advantage that it can be installed on practically all commercially available toilets, so that it can be installed with little effort even on existing toilets. The housing of the bidet consists of a tubular part, in which the individual components of the bidet are inserted, and which is closed with a disk screwed on. The hollow projection of the toilet seat surrounds the tubular housing part and is pivotably mounted on it, so that it can be pivoted upward through about 90.degree. from its horizontal use position. To separate the toilet seat from the bidet for a thorough cleaning of the toilet seat assembly, it is necessary to screw off the cover. Such removal requires trade skill and is therefore often an obstacle to frequent and regular cleaning of the toilet seat assembly, which is desirable for hygienic reasons.